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Behind Glob Top Coatings

With circuit board real estate at a premium and a constant drive to increase production rates and ensure reliable long-term performance, glob tops are one of the options designers are turning to.

A glob top is a precisely measured and applied drop of specially formulated epoxy that is applied over a microelectronic circuit and its connecting wires. Most notably, glob tops are used in chip on board (COB) applications to protect the circuit from contaminants, facilitate thermal dissipation and minimize the thermal mismatch between the chip and substrate. In addition, glob tops provide dielectric insulation for the circuit as well as mechanical support. Glob top adhesives are available as two part epoxies, one part heat curable epoxies and as UV curing systems.

Glob top adhesives are typically thixotropic materials; while they are flowable during application, their viscosity becomes great enough that they do not flow or move after placement. This assures that the epoxy is present at the necessary locations, while at the same time preventing deposits of adhesive from gathering in areas where it could adversely affect the function of delicate assemblies.

Master Bond’s line of glob top materials offers a wide combination of properties to best meet specific PCB design needs. They include both ambient temperature curing systems such as EP21ND and EP51ND, as well as fast curing formulations such as Supreme 3HTND-2GT and Supreme 10AOHT. In addition, Master Bond offers UV curing adhesive systems such as UV15X2GT and UV15-7TK1A, which are also available in dual-cure versions that can cure with UV light and/or heat.